1. Field of the Invention
The present invention relates to a method for the production of highly pure copper thin films by chemical vapor deposition using a novel organic copper compound. More particularly, the present invention relates to a method for the production of highly pure copper thin films free from carbonaceous impurities.
2. Description of the Prior Art
Heretofore, various metal materials have been used as an interconnection material for integrated circuits in the field of electronics. Among them, aluminium has certain advantages, in that it has high electric conductivity, high adhesion to silica and silicon, and is easily used in vapor deposition, etching and pattern formation. However, aluminium is unsuitable for use in the fabrication of ULSI (ultra large scale integrated circuits) due to its low melting point, low electromigration resistance and strong tendency to corrode. Tungsten is interesting as a substitute for aluminium, because of its high electromigration resistance and high melting point. However, tungsten is also unsuitable for the fabrication of ULSI, since a large amount of heat is generated due to its high electric resistance if high current is used to increase the frequency of operation of a ULSI device.
Consequently, interest in this field has recently been focused on the use of copper as an interconnection material. Copper has low electric resistance and high electromigration resistance as well as high conductivity.
A method for producing a metal thin film by chemical vapor deposition, in particular, with an organometallic compound precursor, is of interest since the precursor in gaseous form can be conveniently and inexpensively decomposed into metallic copper and other components thereof, at lower energy to form a metal film on an appropriate surface.
Organic copper compounds containing a .beta.-diketone, alkoxide or cyclopentadiene as a ligand have been Conventionally used as precursors for the vapor deposition of copper films. Most of these precursors, however, have failed to provide highly pure copper thin films because impurities are introduced into the films as a result of the thermal decomposition of the ligands during the vapor deposition. Also, a method is known wherein a .beta.-diketonate compound containing fluorine-substituted .beta.-diketones alone( U.S. Pat. No. 3,356,527) or in combination with a Lewis base (Chemical Materials, 1992, 4, 577, 788) as ligands is employed. However, the fluorine-containing ligands are very expensive and have a marked tendency to corrode equipment, such as reactors.
We, the inventors of the present invention, have conducted intensive studies on various ligands that can be thermally stable at the temperatures at which the precursor is reactive. As a result, we have discovered that an organic copper compound precursor having .beta.-ketoester as a ligand can produce highly pure copper thin films without carbonaceous impurities, and completed the present invention.